Built nearly 20 years ago, the Grand Canyon Skywalk was once the largest glass cantilever bridge in the world and remains one of the most recognizable. The horseshoe-shaped walkway extends 70 feet over the canyon’s edge, sitting 4,000 feet above the Colorado River. While daunting for many who dread the idea of walking on glass thousands of feet above the ground, the skywalk is engineered to hold “70 fully loaded 747 passenger planes,” according to Grand Canyon West, a business enterprise owned by the Hualapai Tribe, which operates the skywalk.
How is that possible? Modern engineering and the strength of glass.
To ensure occupant safety on the Grand Canyon Skywalk, Giroux Glass installed 46 custom multilayer glass panels with four layers of SentryGlas and five layers of Saint-Gobain Diamant glass. The panels are nearly 3 inches thick with a thin glass top layer that can be easily replaced if damaged. A Giroux Glass case study on the project indicates that the panels support the weight of 100 pounds per square foot, enough for more than 120 visitors, and maintain a top safety rating in high winds.
The successful engineering of the Grand Canyon Skywalk helped popularize glass-bottom observation experiences, contributing to a wave of similar attractions worldwide, including the Ledge at Willis Tower in Chicago and immersive decks such as SUMMIT One Vanderbilt in New York City.
Perception vs. Reality
While step-on glazing attractions are designed to provide an immersive experience, offering unobstructed and panoramic views, many people are terrified of stepping over a void, even though they are standing on a solid, though transparent, structure. There are many examples of people crawling, crouching or clinging to guardrails as they traverse glass skywalks because visual perception overrides engineering reality.
“What people are usually reacting to isn’t actual risk, it’s perception,” says Tim Casey, president and owner of California-based TCG Glass. “You can stand on a piece of glass that is structurally performing well within its limits, but if there’s visible deflection, movement or visual distortion, it feels unsafe. That psychological response is real, and it must be addressed in the design.”
David Dunham, P.E., chief sales officer at Texas-based Sentech Architectural Systems, explains that most step-on glazing is designed with triple laminated glass with an added “sacrificial layer.” Though this layer of glass might crack, its failure does not compromise the structural integrity of the entire system, as noted by several high-profile glass breakage incidents at the Sapa Glass Bridge in Vietnam and China’s Yuntaishan Mountain glass walkway. Those incidents highlight the necessity of redundancies to save lives.
That’s because if one ply fails, the remaining plies will support the load, protecting visitors from falling through the glass.
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